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Abstract: FR-PO1119

A Combined Unenhanced Computed Tomography and Biopsy-Based Method for Estimating the Total Nephron Number in Humans

Session Information

Category: Glomerular Diseases

  • 1203 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Sasaki, Takaya, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
  • Tsuboi, Nobuo, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
  • Okabayashi, Yusuke, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
  • Haruhara, Kotaro, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
  • Kanzaki, Go, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
  • Koike, Kentaro, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
  • Kobayashi, Akimitsu, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
  • Yamamoto, Izumi, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
  • Yokoo, Takashi, Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
Background

Methods for estimating the individual total nephron number in the clinical setting may be useful for predicting the progression of renal diseases. Rcently, simple methods have been proposed for estimating the total nephron number by the combined use of enhanced computed tomography (CT) and a renal biopsy in living kidney donors. However, renal disease patients are often not suitable candidates for intravenous contrast media administration. Thus, these methods are limited in daily clinical use for such patients, with further improvements in the methodology required. This study aimed to establish a method of estimating the total nephron number by the combined use of unenhanced CT and biopsy-based stereology.

Methods

We made a model for estimating the renal cortex volume measured by enhanced CT imaging as a true renal cortex volume. Using pre-donation contrast CT angiograms, transplantation donor kidneys were three-dimensionally reconstructed, and the total renal cortical volume was measured. The cortical volume estimates in unenhanced CT were determined by multiplying the semi-automatically measured parenchymal volume and the cortex coefficient. The total nephron number was determined by the combined use of the CT-based cortical volume and the glomerular density per volume in an implantation biopsy. The relative errors were calculated to assess the agreement between the methods.

Results

The values for the parenchymal volume and those for the cortical volume measured in enhanced CT showed a tight correlation (r = 0.949). The cortical to parenchymal volume ratio (0.715) was unaffected by any clinical factors, including age, body size and hypertension, and was defined as the cortex coefficient. The cortical volume and total nephron number estimated by unenhanced CT were consistent with those estimated by enhanced CT, with minimal relative errors (Table).

Conclusion

These results support the feasibility of estimating the total number of nephrons by the combined use of unenhanced CT and biopsy-based stereology, with a possible application for renal disease patients.

 Enhanced CTUnenhanced CTRelative error
Parenchymal volume per kidney125 ± 27 cm3128 ± 29 cm3-0.7 ± 4.5 %
Cortical volume per kidney92 ± 21 cm392 ± 21 cm30.0 ± 10.3 %
Total nephron number per kidney653,000 ± 225,000651,000 ± 215,0000.1 ± 9.2 %